One solution for all-optical switching employs two MEMS devices each containing an array of tiltable micro mirrors, e.g., small mirrors, which can reflect light, which herein refers to any radiation in the wavelength of interest, whether or not in the visible spectrum. An optical path is established for light supplied from an input source, e.g., an optical fiber, to an output, e.g., an output fiber, by steering the light using a first micro mirror on the first optical MEMS device, the first micro mirror being associated with the input fiber, onto a second micro mirror on the second optical MEMS device which is associated with the output fiber. The second micro mirror then steers the light into the output fiber. Each fiber connected to the system is considered a port of the system, the input fibers being the input ports and the output fibers being the output ports.
A problem in the art of all-optical switching using MEMS devices is that in order to increase number of ports in the system, i.e., the number of fibers, it has been necessary to increase the number of micro mirrors employed to perform the switching function. In the prior art, as noted above, the first optical MEMS device contained all of the first micro mirrors integrated thereon and the second optical MEMS device contained all of the second micro mirrors integrated thereon. Since the size of the optical MEMS device is a direct function of the number of micro mirrors on the optical MEMS device, and the number of micro mirrors required is directly proportional to the maximum number of ports available in the all-optical switch, to increase the maximum number of ports available in the all-optical switch requires one to employ a larger optical MEMS device.
Unfortunately, limitations on manufacturing capability and the large package size have effectively limited the optical MEMS device at the present time to 1296 micro mirrors. Furthermore, even if the size of the micro mirrors could be effectively shrunk, there is still a problem in that there needs to be control signals brought to each micro mirror. These control signals consume large amounts of space on the optical MEMS device, which would thus result in the optical MEMS device being very large. Additionally, there are control signals for each micro mirror that must be brought to the optical MEMS device from off of its substrate. In order to make these connections, additional large amounts of space is required on the optical MEMS device.
As a result of all these space requirements, the optical MEMS chip is quite large, and so, due to the manufacturing capability limits, the number of micro mirrors that can be placed on a single optical MEMS device is limited. The limitation on the number of micro mirrors, in turn, limits the number of ports of an all-optical switch.
Additionally, the micro mirrors presently available have a limited effective range through which they can be tilted. The limitation on the effective range further limits the number of ports that can be implemented in an all-optical switch employing such optical MEMS devices because each micro mirror on the first optical MEMS device must be able to direct the light incident on it to each of the micro mirrors on the second optical MEMS device. The ability to so direct the light is a function of the effective tilt range of the micro mirrors. In other words, greater effective tilt angle allows each micro mirror to direct its light over a greater area. For optical MEMS devices arranged as an optical switch the greatest tilt angle required is for connections between micro mirrors in the opposing corners of the optical MEMS devices. For example, the most tilt is required by a micro mirror at the top right of the first MEMS device which must direct its light to a micro mirror at the bottom left of the second MEMS device. Thus, the size of the micro mirror array that can be employed in an optical switch is limited by the effective tilt range of its optical MEMS devices.
While increasing the separation distance between the two optical MEMS devices decreases the required tilt angle, which would allow the use of larger micro mirror arrays without changing the effective tilt range of the micro mirrors, doing so suffers from the disadvantage that it increases the beam diffraction, which thus requires the use of a micro mirror with a larger diameter or results in a loss of some of the light. Since using a larger micro mirror with present technology requires additional space, doing so increases the distance between the micro mirrors on the optical MEMS device, which further increases the size of the optical MEMS device for the same number of micro mirrors. As a result of increasing the size of the optical MEMS device, a greater tilt angle is required to couple the opposing corners of the opposing optical MEMS devices. Thus, essentially, additional separation of the opposing optical MEMS devices does not help to increase the number of ports due to the limited available tilt angle.